This invention relates to a thermal (heat-sensitive) transfer recording medium, more particularly to a thermal transfer recording medium capable of printing with high transfer sensitivity and with low energy, and also inhibiting generation of ground contamination (fog) on a recording sheet such as low smoothness paper and giving a dye transferred image with excellent fixability on a recording sheet and also high resolving power.
Thermal transfer recording medium has been used in the prior art as a recording medium for forming by transfer an image on a recording sheet such as plain paper by a thermal printer or a thermal facsimile.
Such a thermal transfer recording medium has at least one colorant layer on a support. As the colorant layer, there have been known layers containing colorants comprising dyes such as pigments and heat-fusible substances which are low melting substances such as waxes. Also, as the support, for obtaining good reproducibility of the dye transferred image obtained from the colorant layer coated thereon, films excellent in surface smoothness and dimensional stability have been used.
The thermal transfer recording medium of this kind in the prior art has been variously devised and proposed so as to effect transfer printed images sharply with good fixability onto the recording sheet with a smooth surface.
However, at the present time, it has been strongly demanded to have a thermal transfer recording medium which can also effect good transfer of printed images onto the so-called low smoothness surface which is not necessarily smooth on the surface.
For, in the case of performing, for example, a trial printing of a document by a thermal printer having a thermal head, it is not necessary at all to use an expensive smooth paper, but rather an inexpensive recording sheet with low smoothness may be desirably employed, and it is frequently practiced to use the back surface (this surface is usually a rough surface) of a plain paper of which a printed image is printed on the front surface, but has now become unnecessary. Also, for prevention of forgery of documents, or for presenting the specific feature of the addresser of the documents, it is sometimes necessary to transfer the printed images onto a recording sheet which has been intentionally made to have low smoothness surface. Besides, it is not only sufficient that printed images can be anyhow transferred onto low smoothness surface, but it has been increasingly required to form printed images onto a recording sheet of which surface is specially made rough with a thermal transfer recording medium with high transfer sensitivity, low energy, without generation of ground contamination (fog), and with good fixability and high resolving power.
In spite of such demands, various inventions and utility models concerning the ink layers in thermal transfer recording medium have been in most cases directed to plain papers with smooth surface, and it is not too much to say that substantially no thermal transfer recording medium has been proposed provided with an ink layer satisfying all of the increasing requirements as mentioned above.